1. Field of the Disclosure
This specification relates to a gas insulated switchgear (GIS), and particularly, to a structure of a three-phase integrated bus in a GIS.
2. Background of the Disclosure
A gas insulated switchgear (GIS) is an electric device, which is installed in a circuit between a power supply side and a load side of an electric power system, to protect the electric power system and a load device by safely cutting off a current when the circuit is artificially switched on or off in a normal current-flowing state or when a fault current such as ground circuit or short-circuit is generated on the circuit. The GIS generally includes a bushing unit for receiving power from a high voltage power supply, a line disconnector switch/earthing switch (DS/ES), a gas circuit breaker, a bus DS/ES, a driving unit, a controller and the like.
The GIS occupies a great space. Therefore, one of important design requirements for the GIS is that each component is compactly disposed, exhibits a necessary performance, and is suitable for conditions.
From this perspective, a bus used in the GIS has to meet conflictive design conditions, namely, ensuring of an insulating performance and a compact construction.
Specifically, unlike a three-phase separated bus, a three-phase integrated bus has three phase conductors coexisting within one enclosure. Therefore, the ensuring of the insulating performance and the compact construction are more important design factors in the three-phase integrated bus.
As basic types of buses, FIG. 1 shows a parallel type bus and FIG. 2 shows a straight pipe type bus. A structure of a three-phase integrated bus is shown in FIG. 1. Referring to FIG. 1, spacers 5 are coupled to both sides of an enclosure 1 with a cylindrical shape, three phase conductors 2, 3 and 4 are fixed to the spacers 5 at positions of three apexes of an inverted triangle, respectively. Each of the three phase conductors 2, 3 and 4 has both sides bent. Here, middle portions of the three phase conductors 2, 3 and 4 are disposed in parallel to one another, and a branch bus is upwardly led out (upwardly extending) from a part of each of the three phase conductors 2, 3 and 4. In order to meet minimum insulating distances between the adjacent conductors and between each conductor and the enclosure, the enclosure has to be considerably increased in size.
On the other hand, the straight pipe type bus shown in FIG. 2 includes three phase conductors, 2′, 3′ and 4′ formed in a shape of straight pipe within a cylindrical enclosure 1′ and disposed in parallel into a form of an inverted triangle. Here, the second phase conductor 3′ and the third phase conductor 4′ may be orthogonal to a branch bus of the first phase conductor 2′ at their middle portions. To ensure insulating distances among them, each phase conductor has to be arranged with a sufficient distance. This shows that a considerable space even up to both sides of the three phase conductors 2′, 3′ and 4′ is consumed.
U.S. Pat. No. 6,509,522, as an exemplary prior art having the straight pipe type conductors and the cylindrical enclosure, has introduced “Three phase Integrated Gas Insulated Bus.” This invention provides a bus structure that each phase has two outlets branched in a vertical direction and in a horizontal direction. However, the three phase conductors are basically designed in a shape of straight pipe to be arranged in parallel in a triangular form, and the enclosure has the cylindrical shape.
Meanwhile, referring to Gas Insulated Bus and GIS published in Korean Patent Application Laid-Open Publication No. 1999-023397A, for a compact construction of a bus, three phase conductors are formed to be convex along a circumferential direction. However, such shape is difficult to be produced and the enclosure still has the cylindrical shape. Consequently, it is substantially difficult to expect a compact arrangement effect of the three phase conductors.